Opperman's car was found illegally parked on a street in Vermillion, South Dakota, in the early morning hours of December 10, 1973.

He appealed, and the Supreme Court of South Dakota reversed his conviction on the grounds that the inventory search was an unreasonable one under the Fourth Amendment.

"To permit the uninterrupted flow of traffic and in some circumstances to preserve evidence, disabled or damaged vehicles will often be removed from the highways or streets at the behest of police engaged solely in caretaking and traffic-control activities.

Police will also frequently remove and impound automobiles which violate parking ordinances and which thereby jeopardize both the public safety and the efficient movement of vehicular traffic."

By the time of the Opperman decision, a number of state and federal courts had already sustained these practices against challenges that they engendered "unreasonable" searches and seizures that violate the Fourth Amendment.

"[1] Inventory searches of automobiles must necessarily extend to the trunk and the glove compartment, since these are places where people keep important documents and valuables.

Furthermore, the court had already sanctioned an inventory search of an impounded car suspected to contain the service revolver of a fugitive Chicago police officer.

Looking in the glove compartment for valuables seemed excessive in light of the other legal protections afforded "gratuitous depositors" under South Dakota law.

If the police were to dispense with the consent requirement, a specific reason must exist to believe that this car contained "particular valuable property threatened by the impoundment."

But Justice Marshall saw no such specific evidence in the record in this case, because the owner was apparently content to leave the car parked on the street and the other items that were in plain view did not suggest that anything of particular value would be in the glove compartment.